diff --git a/benchmarks/src/main/scala/io/bullet/borer/benchmarks/JsoniterScalaDefinitions.scala b/benchmarks/src/main/scala/io/bullet/borer/benchmarks/JsoniterScalaDefinitions.scala
index 22309d55..e311f64c 100644
--- a/benchmarks/src/main/scala/io/bullet/borer/benchmarks/JsoniterScalaDefinitions.scala
+++ b/benchmarks/src/main/scala/io/bullet/borer/benchmarks/JsoniterScalaDefinitions.scala
@@ -59,36 +59,45 @@ class JsoniterScalaModelBenchmark extends DomBenchmark {
 
   private var codec: JsonValueCodec[Product] = _
 
-  def nullable[T: JsonValueCodec: Default]: JsonValueCodec[Nullable[T]] = {
-    new JsonValueCodec[Nullable[T]] {
-      override def decodeValue(in: JsonReader, default: Nullable[T]): Nullable[T] =
-        if (in.isNextToken('n')) in.readNullOrError(default, "expected JSON value or null")
-        else {
-          in.rollbackToken()
-          implicitly[JsonValueCodec[T]].decodeValue(in, default.value)
-        }
-
-      override def encodeValue(x: Nullable[T], out: JsonWriter): Unit =
-        if (x.value == null) out.writeNull()
-        else implicitly[JsonValueCodec[T]].encodeValue(x.value, out)
-
-      override def nullValue: Nullable[T] = new Nullable(Default.get[T])
-    }
-  }
+  implicit val nullableDoubleCodec: JsonValueCodec[Nullable[Double]] = new JsonValueCodec[Nullable[Double]] {
+    override def decodeValue(in: JsonReader, default: Nullable[Double]): Nullable[Double] =
+      if (in.isNextToken('n')) in.readNullOrError(default, "expected Double or Null")
+      else {
+        in.rollbackToken()
+        in.readDouble()
+      }
+
+    override def encodeValue(x: Nullable[Double], out: JsonWriter): Unit = out.writeVal(x.value)
 
-  implicit val nullableDoubleCodec: JsonValueCodec[Nullable[Double]] = {
-    implicit val c: JsonValueCodec[Double] = JsonCodecMaker.make(CodecMakerConfig())
-    nullable[Double]
+    override val nullValue: Nullable[Double] = new Nullable(Default.get[Double])
   }
 
-  implicit val nullableIntCodec: JsonValueCodec[Nullable[Int]] = {
-    implicit val c: JsonValueCodec[Int] = JsonCodecMaker.make(CodecMakerConfig())
-    nullable[Int]
+  implicit val nullableIntCodec: JsonValueCodec[Nullable[Int]] = new JsonValueCodec[Nullable[Int]] {
+    override def decodeValue(in: JsonReader, default: Nullable[Int]): Nullable[Int] =
+      if (in.isNextToken('n')) in.readNullOrError(default, "expected Int or Null")
+      else {
+        in.rollbackToken()
+        new Nullable(in.readInt())
+      }
+
+    override def encodeValue(x: Nullable[Int], out: JsonWriter): Unit = out.writeVal(x.value)
+
+    override val nullValue: Nullable[Int] = new Nullable(Default.get[Int])
   }
 
-  implicit val nullableStringCodec: JsonValueCodec[Nullable[String]] = {
-    implicit val c: JsonValueCodec[String] = JsonCodecMaker.make(CodecMakerConfig())
-    nullable[String]
+  implicit val nullableStringCodec: JsonValueCodec[Nullable[String]] = new JsonValueCodec[Nullable[String]] {
+    override def decodeValue(in: JsonReader, default: Nullable[String]): Nullable[String] =
+      if (in.isNextToken('n')) in.readNullOrError(default, "expected Int or Null")
+      else {
+        in.rollbackToken()
+        new Nullable(in.readString(null))
+      }
+
+    override def encodeValue(x: Nullable[String], out: JsonWriter): Unit =
+      if (x.value == null) out.writeNull()
+      else out.writeVal(x.value)
+
+    override val nullValue: Nullable[String] = new Nullable(Default.get[String])
   }
 
   def setup(): Unit = {